XML 56 R41.htm IDEA: XBRL DOCUMENT v3.8.0.1
Revenue - Air Traffic Liability Rollforward (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Deferred Revenue Arrangement [Line Items]    
Other Revenue, Net $ 317 $ 266
Air Traffic Liability Roll Forward    
ATL, beginning balance 4,565 4,221
Current Period Sales 5,403 5,415
Revenue amounts in beginning balance [1] (1,827) (1,701)
Revenue from Current Period Sales [1] (2,711) (2,796)
ATL, ending balance $ 5,430 $ 5,139
[1] (a) Does not include certain ancillary revenues that are purchased on the day of travel, which do not flow through Air traffic liability.